Lift truck



H. w. HOSBEJN ETAL 3,127,956

April 1, 1964 LIFT TRUCK 3 Sheets$heet 1 Original Filed Feb. 25, 1954INVENTORS. HUGH W. HOSBEIN ROBERT LAPSLEY ATTY ' April 7, 1964 H. w.HOS'BEIN ETAL 3,127,956

LIFT TRUCK Original Filed Feb. 25, 1954 s sheets-sheet 2 INVENTORS. HUGHW. HOSBEIN ROBERT. LAPSLEY ATTY.

Apr 7, 1964 H. w. HOSBEIN ETAL- 3,127,956

LIFT TRUCK Original Filed Feb. 25, 1954 3 Sheets-Sheet 3 FIG. 3

INVENTORS HUGH W. HOSBEIN ROBERT LAPSLEY ATTY.

United States Patent 3,127,956 LIFT TRUCK Hugh W. Hosbein, Niles, andRobert Lapsley, Berrien Springs, Mich, assignors to Clark EquipmentCompany, a corporation of Michigan ()riginal application Feb. 25', I954,Ser. No. 412,439. Divided and this application Nov. 16, 1961, Ser. No.163,063

6 Claims. (ill. 187-9) Our present invention relates generally to lifttrucks, and more specifically, to a telescopic mast assembly for lifttrucks. This is a divisional application of application Serial No.412,439, filed February 25, 1954, now abandoned.

Our present invention is particularly concerned with a telescopic mastassembly which comprises an outer upright guideway that is mounted onthe truck frame, and an inner upright guideway that is slidably mountedin the outer upright guideway. The inner upright guideway is adapted toreceive and support a vertically movable load supporting carriage.

One feature of our present invention resides in the provision of atelescopic hydraulic assembly which comprises inner, intermediate andouter cylinders, with at least two of them being actuatable successivelyvertically.

Another feature of our present invention resides in the arrangement ofthe cylinders of the hydraulic assembly which causes fluid admitted tothe latter to move first the outer cylinder relative to the inner andintermediate cylinders and thereafter the intermediate and outercylinders relative to the inner cylinder.

It is still another object of our present invention to provide a mastassembly which will not interfere with the truck operators vision in aforward direction.

In accomplishing the latter object, we provide a pair of multiplecylinder hydraulic assemblies, with one being arranged at either side ofthe truck immediately forwardly of the inner and outer uprights. Byproviding spaced hydraulic assemblies at either side of the truck,rather than a single hydraulic assembly intermediate of the uprights,the operators vision in a forward direction is improved considerably.

It is a further object of our present invention to provide a mastassembly wherein the elements thereof are so arranged that thecounterweight required at the rear of the vehicle may be decreasedwithout sacrificing load capacity.

The afore-noted object is accomplished by arranging the center ofgravity of the mast assembly rearwardly of the axis of rotation of theforward vehicle wheels for decreasing the moment acting at the forwardend of the truck and thus permitting a lighter counter-weight to beemployed at the rear of the vehicle. More specifically, the inner andouter uprights are arranged rearwardly of the axis of rotation of theforward vehicle wheels while the pair of hydraulic assemblies arearranged forwardly of the axis of rotation of the forward vehiclewheels. In this construction, the load supporting carriage is providedwith forwardly extending support members which are movable verticallyintermediate of the pair of hydraulic assemblies.

Now, in order to acquaint those skilled in the art with the manner ofconstructing and using mast assemblies in accordance with the principlesof our present invention, we shall describe in connection with theaccompanying drawings, preferred embodiments of our invention.

In the drawings:

FIGURE 1 is a partial side elevational view of a lift truck whichembodies our present invention;

FIGURE 2 is a partial plan view of the mast assembly shown in FIGURE 1;and

3,127,956 Patented Apr. 7, 1964 "ice FIGURE 3 is an enlarged verticalsectional view, with portions being broken away for the sake of clarity,showing the hydraulic assembly of our present invention.

Referring now to FIGURES 1 and 2, we shall describe a preferredembodiment of our present invention. The reference numeral 78 indicatesa rider type industrial truck which comprises a main frame 86 that issupported at its forward end on a pair of spaced rotatable groundengaging wheels 82 which in this case may be the drive wheels. Thewheels 82 are journalled at the outer ends of a transversely extendingaxle housing 84 which is secured in a known manner in bracket portions86 of the main frame 80. The housing 84, immediately inwardly of thebracket portions 86, at each side of the truck, supports frame members88 which extend downwardly and then project forwardly and rearwardly.The rearward ends of the frame members 88 support the lower end of anupright assembly 20.

The upright assembly 20 comprises a pair of spaced channel members 22,constituting an outer upright guideway, which have slidably mountedtherein channel members 34, constituting an inner upright guideway.Mounted for vertical movement within the upright assembly 20 is a loadsupporting carriage 90 which includes horizontally spaced forwardlyextending support members having secured to their forward ends atransverse plate 92. The plate 92, in turn, supports L-shaped forkframes 38 or any other load gripping or carrying attachment. The rearends of the support members of the carriage 90 are provided with rollers40 which have rolling contact with the inner upright guideway 34.

Relative movement between the carriage 90, the inner upright 34 and theouter upright 22 is adapted to be effected by means of a pair ofhydraulic assemblies indicated generally at 42. The assemblies 42 aresupported at their lower ends on the forward ends of the frame members88 and are stabilized at their upper ends by brace means 93. Each of thehydraulic assemblies 42 comprises three concentric cylinders with theouter and intermediate cylinders being actuatable successivelyvertically as will be described in detail below. The upper ends of theouter cylinders 48 carry rotatable sprockets 94 over which are trainedchains 64. The chains 64 are secured at their one ends to verticallyextending rods 96 which at their lower ends are anchored by brackets tothe lower ends of the intermediate cylinders of the hydraulic assemblies42. The other ends of the chains 64 are suitably secured at 98 to theload supporting carriage 96. As best shown in FIGURE 2, the loadsupporting carriage projects forwardly between the pair of hydraulicassemblies 42.

Referring to FIGURE 3, each of the pair of hydraulic assemblies 42, ingeneral, comprises a plurality of relatively movable elements, and, morespecifically, comprises three concentric cylinders 44', 46 and 48, withthe outer and intermediate cylinders being actuatable successivelyvertically. Each inner cylinder 44, at its lower end, is mounted uponthe forward end of the respective support frame member 88.

As shown in FIGURE 3, the lower end of the inner cylinder 44 is formedwith a port 52 through which fluid may be admitted to the interiorthereof. The truck 78 is provided with fluid pressure developing means(not shown) and fluid is transmitted to the port 52 through a hose line(not shown) with the fluid flow being controlled remotely by theoperator of the truck 78.

The lower end of the intermediate cylinder 46 is provided with sealmeans 54 which not only serves to prevent fluid leakage the-repast, butalso, upon extension of the intermediate cylinder 4-6, engages the stopmeans 56 at the upper end of the inner cylinder 44 for limiting theupward travel of the intermediate cylinder. The lower end of the outercylinder 48 is correspondingly fitted with seal means 58 which bothprevents fluid leakage therepast and, upon extension of the outercylinder 48, engages the stop means 60 at the upper end of theintermediate cylinder 46, for causing the intermediate cylinder to moveconjointly with the outer cylinder. The outer cylinder 48 is firstmovable vertically relative to the inner and intermediate cylinders 44and 46, and thereafter the intermediate and outer cylinders 46 and 48move conjointly relative to the inner cylinder 44.

The upper end of the outer cylinder 48 is closed and serves as a crosshead for supporting pulley means comprising the rotatable sprocket 94over which is trained chain 64-, as explained above. The chains 64 serveto raise the carriage 90 to the upper end of the inner upright. 64 andthereafter conjointly raise the inner upright 34- and carriage 96 withinthe outer upright 22.

In the operation of the mast assembly of our present invention, fluidunder pressure may be selectively admitted to the ports 52 formed in theinner cylinders 44' of the hydraulic assemblies 42. The fluid is forcedupwardly within the inner cylinders 44 and exerts an up ward pressure onthe closed end of the outer cylinders 48 where-upon the latter are movedupwardly relative to the inner and intermediate cylinders 44 and 46. Asthe outer cylinders 48 move upwardly, the chains 64 ride over thesprockets 94 and move the load supporting carriage 90 upwardly withinthe inner upright 22. The load supporting carriage 9% moves at a 2:1ratio relative to the movement of the outer cylinder 48 of the hydraulicassembly in a well-known manner.

When the load supporting carriage 99 reaches the top of the innerupright 34-, the carriage contacts a cross member, not shown, which isconnected across the top edges of upright channels 34, and causes theinner upright to move upwardly conjointly with the carriage relative tothe outer upright 22. During this upward movement of the load supportingcarriage 9t and the inner upright 34, the seal means 58 at the bottom ofeach outer cylinder 43 engages the stop means 60 at the upper end ofeach intermediate cylinder 46 and serves to draw the intermediatecylinder 46 upwardly conjointly with the outer cylinder. Coniointmovement of the intermediate and outer cylinders 46 and 48 may continueuntil the seal means 54 at the bottom of the intermediate cylinder 46engages the stop means 56 at the upper end of the inner cylinder 44.

It is to be noted that the rods 96 to which the one ends of the chains64 are secured, move upwardly conjointly with the intermediatecylinders. Consequently after each outer cylinder 48 has been moved tothe limit of its movetrnent relative to the intermediate 46, the outerand intermediate cylinders and the carriage thereafter move conjointly.From the foregoing description, it will be apparent that we haveprovided a mast assembly wherein the load supporting carriage movesvertically first at a 2:1 ratio relative to the movement of thehydraulic assembly and then at a 1:1 ratio. By employing the two ratiosof movement in this manner, the over-all height of the mast assembly atany given vertical position of the load supporting carriage ismaintained at a minimum.

In order to achieve the operation just described, it is essential thatthe cylinders 44, 46 and 48 of each assembly 42 be of the correctdimensions to assure that the intermediate cylinder 46 will not start torise before the outer cylinder 48. It will be understood that the forcepushing up on cylinder 48 is proportional to the area defined by theprojection of the inside margin of sealing means 53 on the end ofcylinder 48. Simultaneously a force acts downwardly on the intermediatecylinder which is proportional to the area defined by the inside marginof sealing means 58 minus an area equal to that defined by the innermargin of sealing means 54. This downward force must be greater than onehalf of the larger force pushing upwardly on cylinder 48' because onehalf of the larger force acts through the chain 64 on the bracket whichconnects the intermediate cylinder to rod 96 while the other half actson the carriage 90. Therefore, if the mechanism is properlyproportioned, the force pushing down the intermediate cylinder willexceed the force exerted by chain 64 onrod 96 tending to cause cylinder46 to rise, and the outer cylinder 48 will rise first.

The mechanism would operate if the intermediate cylinders started torise first, but it would not provide a large free lift as it doesotherwise (free lift being defined as the maxim-um fork heightattainable without any increase in the over-all height of the machine).It will be understood that if the carriage moved upwardly conjointlywith the hydraulic assemblies 42, as would be the case if theintermediate cylinders moved first, the top of the hydraulic assemblies(that is, the closed upper surface of cylinders 43) would contact theabove-mentioned cross member which connects the top of channels 34 andstart the inner upright moving upwardly while the carriage and forkswere still at a comparatively loW level. However, when the outercylinders move first, the carriage and forks move upwardly at a 2:1ratio with respect to the hydraulic assemblies, so that the carriage andforks can move upwardly much farther before any increase occurs in theover-all height of the machine.

In understanding the foregoing explanation of forces acting on thevarious cylinders, it should be understood that stops 56 and 6t? arearranged to admit fluid under pressure down between the inner andintermediate cylinders and between the intermediate and outer cylinders.

When it is desired to lower the load supporting carriage 9% from itsmaximum elevation to the position shown in FIGURE 1, the fluid underpressure need only be bled from the inner hydraulic cylinders 44,through the ports 52. This permits the weight of the elements of theupright assembly and load to force the intermediate and outer cylindersof the hydraulic assemblies downwardly while the carriage 9% ispermitted to be lowered at the end of the chains 64 until the uprightand hydraulic assemblies 34 and 42 are fully nested as illustrated.

The device 63 in cylinder 44 near the top of the cylinder is a howregulator, or flow control device, which may be employed if desired.This device varies the rate of fluid flow out of the hydraulic assembly,dependent upon the hydraulic pressure. It is arranged so that the flowvaries inversely with the pressure. Hence the heavier the load on thefork the slower the lowering speed of the forks. This device serves as asafety device to prevent rapid descent of a load in the event of a breakin the hydraulic line between the hydrauiic assembly and the controlvalve. It also prevents incorrect operation of the mechanism by loweringa heavy load too rapidly.

It will be quickly recognized by those skilled in the art that since apair of hydraulic actuating assemblies 42 are provided, with one beingarranged at either side of the truck, the visibility of the operator ofthe vehicle is not impaired when he is looking forwardly as he can viewthe load or the area in front of the truck by looking between theupright members and the hydraulic assemblies. It is to be further notedthat the elements of the mast are arranged so that the center of gravitythereof lies rearwardly of the axis of rotation of the drive wheels 82.This arrangement stabilizes the vehicle and permits a relatively lightercounterweight to be employed at the rear end of the vehicle.

Now while we have shown and described what We believe to be a preferredembodiment of our present invention, it will be understood that variousrearrangements and modifications may be made therein without departingfrom the spirit and scope of our invention.

We claim:

1. In a lift truck having a main frame and a pair of transversely spacedground engaging wheels mounted adjacent the forward end of the frame,the combination of an upright assembly comprising an outer uprightguideway including transversely spaced channeled members and an innerupright guideway including transversely spaced channeled members, thelongitudinal center line of the upright assembly lying rearwardly of theaxis of rotation of said wheels, a load supporting carriage supported byand vertically movable in said inner upright guideway, a pair oftransversely spaced hydraulic assemblies carried at the forward end ofthe main frame and arranged forwardly of and substantially in line withthe channeled members of the outer upright guideway and rearwardly ofsaid carriage, each of said hydraulic assemblies comprising relativelyvertically movable elements, and means associated with said carriage andsaid hydraulic assemblies for moving said carriage relative to saidinner upright guideway and said inner upright guideway relative to saidouter upright guideway upon actuation of said hydraulic assemblies.

2. In a lift truck having a main frame, transversely spaced groundengaging rotatable wheels at the forward end thereof, the combination ofa single upright assembly carried by the main frame rearwardly of theaxis of rotation of the rotatable Wheels, a load supporting carriagesupported from and vertically movable in said upright assembly, a pairof transversely spaced hydraulic assemblies carried by the main frameforwardly of the axis of rotation of said rotatable wheels, saidcarriage being supported forwardly of said hydraulic assemblies, andmeans associated with said carriage and said hydraulic assembly formoving said carriage relative to said upright assembly upon actuation ofsaid hydraulic assembly.

3. In a lift truck having a main frame, transversely spaced groundengaging rotatable wheels at the forward end thereof, the combination ofan upright assembly carried by the main frame rearwardly of the axis ofrotation of the rotatable wheels, said upright assembly comprising anouter upright guideway and an inner upright guideway, a pair ofhydraulic assemblies one being arranged on either side of the truckforwardly of the axis of rotation of said rotatable wheels, a loadsupporting carriage vertically movable in said inner upright guidewayand extending forwardly between said hydraulic assemblies, and meansassociated with said carriage and said hydraulic assemblies for movingsaid carriage relative to said inner upright guideway and said innerupright guideway relative to said outer upright guideway upon actuationof said hydraulic assemblies.

4. In a lift truck having a main frame, transversely spaced groundengaging rotatable wheels at the forward end thereof, the combination ofan upright assembly carried by the main frame rearwardly of the axis ofrotation of said rotatable wheels, said upright assembly comprising anouter upright guideway including a pair of transversely spaced channelmembers and an inner upright guideway including a pair of transverselyspaced channel members, a pair of hydraulic assemblies carried by themain frame forwardly of the axis of rotation of the rotatable wheelswith the hydraulic assemblies being arranged substantially in line withthe channel members of said outer upright guideway, a load supportingcarriage vertically movable in said inner upright guideway andprojecting forwardly between said pair of hydraulic assemblies, each ofsaid hydraulic assemblies comprising inner, intermediate and outerconcentric cylinders with the latter two cylinders being actuatablesuccessively vertically, and means including sprocket and chain meansassociated with said carriage and said hydraulic assemblies for raisingsaid carriage to the upper end of said inner upright and thereafterconjointly raising said inner upright and carriage within said outerupright upon actuation of said hydraulic assemblies.

5. In a lift truck having a main frame including a pair of transverselyspaced longitudinally extending frame members and a transverse wheeledaxle means support ing said frame members adjacent the forward endsthereof, an upright mast structure forming guideways supported from saidaxle means at a location spaced longitudinally rearwardly of said axlemeans, a pair of transversely spaced hoist motor means supported by saidaxle means and spaced longitudinally forwardly of said mast structure,load carrying means supported in said mast structure for verticalmovement relative thereto and spaced longitudinally forwardly of saidhoist motor means, and means interconnecting said load carrying means,said hoist motor means and said mast structure such that actuation ofsaid hoist motor means effects elevating movement of said load carryingmeans in said mast structure.

6. A lift truck as claimed in claim 5 wherein longitudinally extendingbracket means are connected between said mast structure and said loadcarrying means, roller means connect said bracket means to said maststructure, and said pair of hoist motor means are spaced transversely insubstantial longitudinal alignment with opposite sides of said maststructure.

References Cited in the file of this patent UNITED STATES PATENTS1,725,624 Dixon Aug. 20, 1929 2,156,204 Stolze Apr. 25, 1939 2,456,320Repke Dec. 14, 1948 2,545,417 Ulinski Mar. 13, 1951 2,623,653 FramheinDec. 30, 1952 2,627,943 Hastings Feb. 10, 1953 2,634,587 Ptak Apr. 14,1953 2,645,306 Turner July 14, 1953 2,653,678 Lehrman Sept. 29, 19532,666,501 Abbe Jan. 19, 1954 2,670,811 Shaffer Mar. 2, 1954 2,738,087Arnot Mar. 13, 1956 2,929,524 Carlson et al. Mar. 22, 1960

1. IN A LIFT TRUCK HAVING A MAIN FRAME AND A PAIR OF TRANSVERSELY SPACEDGROUND ENGAGING WHEELS MOUNTED ADJACENT THE FORWARD END OF THE FRAME,THE COMBINATION OF AN UPRIGHT ASSEMBLY COMPRISING AN OUTER UPRIGHTGUIDEWAY INCLUDING TRANSVERSELY SPACED CHANELED MEMBERS AND AN INNERUPRIGHT GUIDEWAY INCLUDING TRANSVERSELY SPACED CHANNELED MEMBERS, THELONGITUDINAL CENTER LINE OF THE UPRIGHT ASSEMBLY LYING REARWARDLY OF THEAXIS OF ROTATION OF SAID WHEELS, A LOAD SUPPORTING CARRIAGE SUPPORTED BYA VERTICALLY MOVABLE IN SAID INNER UPRIGHT GUIDEWAY, A PAIR OFTRANSVERSELY SPACED HYDRAULIC ASSEMBLIES CARRIED AT THE FORWARD END OFTHE MAIN FRAME AND ARRANGED FORWARDLY OF AND SUBSTANTIALLY IN LINE WITHTHE CHANNELED MEMBERS OF THE OUTER UPRIGHT GUIDEWAY AND REARWARDLY OFSAID CARRIAGE, EACH OF SAID HYDRAULIC ASSEMBLIES COMPRISING RELATIVELYVERTICALLY MOVABLE ELEMENTS, AND MEANS ASSOCIATED WITH SAID CARRIAGE ANDSAID HYDRAULIC ASSEMBLIES FOR MOVING SAID CARRIAGE RELATIVE TO SAIDINNER UPRIGHT GUIDEWAY AND SAID INNER UPRIGHT GUIDEWAY RELATIVE TO SAIDOUTER UPRIGHT GUIDEWAY UPON ACTUATION OF SAID HYDRAULIC ASSEMBLIES.